Indoor positioning systems are capable of pinpointing the location of a device in an indoor space where GPS is not available. One possible way to identify device locations is to use Wi-Fi signatures. Wi-Fi signatures consist of a list of which Wi-Fi access points are visible and each of their signal strengths at a given physical location. A typical Wi-Fi based indoor positioning system identifies the current position of a device by comparing the Wi-Fi signatures measured by the device with Wi-Fi signatures at known locations collected during a calibration phase.
In practice, the collection of this calibration data is very onerous since it requires an individual to walk around the space being calibrated while frequently (every meter or so) marking the individual's location on a map, so that the Wi-Fi signatures being recorded can be associated with known locations. Even if automated methods can be used to occasionally pinpoint automatically the location of the calibrating user (e.g., proximity to an RFID tag present at a known location), these known locations do not appear with sufficient resolution in the indoor space, so the user is still required to mark its position frequently.